Answer
The word "Bhagavan" is used quite loosely in Hindu Dharma. Sometimes it is used for Ishvara (God), sometimes for Devatas (celestial beings), and sometimes even for human beings. For instance, Bhagavan Hanuman, Bhagavan Ganapati — these are Devatas, not Ishvara. Similarly, Bhagavan Shankaracharya, Bhagavan Rajneesh — their respective devotees and followers also refer to them as Bhagavan.
However, your intention is probably not about Devatas or human beings, but about Ishvara.
The word Ishvara is also used in two ways in Hindu Dharma. First, for Parameshvara, who is Nirakara (formless) — that is, for ParaBrahman. Second, for the Saguna (with attributes) form of ParaBrahman, namely Narayana (Shri Vishnu), who governs the creation. On one hand, Narayana is called "Saguna Brahman," and on the other, He is called "Ishvara." He is called Saguna Brahman because when creation takes place, ParaBrahman brings it forth through Para Prakriti. Prakriti is constituted of three Gunas, and therefore everything in creation necessarily contains the Gunas of Prakriti. ParaBrahman is beyond the Gunas of Prakriti — He is Trigunatita (transcending the three Gunas). But when the same ParaBrahman manifests in a Sakara (embodied) form, as Narayana, He manifests by assuming the Gunas of Prakriti. Bhagavan Narayana embodies pure Sattva Guna.
So, if we take the precise meaning of Ishvara, it refers to Bhagavan Narayana.
You have already clarified that you are asking not about an avatar form, but whether Ishvara Himself can grant darshana (divine vision) in an embodied form.
So I take your question to mean: does Bhagavan Narayana or Bhagavan Vishnu grant darshana in His physical body — that is, in a tangible form — or not?
Here, another distinction needs to be understood. The visible body of Bhagavan is not a material body, because it is not composed of the five gross elements (Pancha Bhutas). It is a divine body (Divya Sharira), but it can be seen and touched.
Even the devotees who go to Vaikuntha (the abode of Bhagavan Vishnu) do not go there with a material body. They do possess a "body" in Vaikuntha, but it is a divine body of that celestial realm. A body made of the five gross elements is perishable. A divine body is not perishable.
Having given these clarifications, the answer to your question is this: Bhagavan, in His form as Ishvara, does grant darshana to His devotees with His divine body. This is known not only from the Shastras (scriptures) but also from the personal experiences of saints and sages. For example, Seth Jaydayal Goyandka, the founder of Gita Press, who is no longer on this earth, was granted embodied darshana by Bhagavan Vishnu on several occasions. His colleague at Gita Press, Shri Hanuman Prasad Poddar ji, was also granted embodied darshana by Bhagavan Narayana at least twice. Both of these great souls have described the full experience of those darshanas. In my detailed commentary on the Bhagavad Gita, which is available with some members of this group — "Mokshavidyadayini Param Pavan Bhagavad Gita" — the experiences of these great souls' darshanas are discussed in their own words. If we look at the Puranas, the devotee Dhruva was granted embodied darshana by Bhagavan Narayana.
My detailed commentary on the Bhagavad Gita is available at inlightofgita.org. This website is currently under construction, but the study of the Gita can be undertaken on it. www.gitaglobalfamily.org is also worth visiting.