Can I do śrāddha for my maternal grandparents (mother's side)?

yes — the maternal line (mātāmaha) is part of śrāddha, and a daughter's child often performs it when there is no one else.

Classical śrāddha already includes the mother's side: in many forms, offerings go to three generations of the father's line and three of the mother's father's line (mātāmaha, pramātāmaha and so on). So remembering your nānā and nānī is not unusual — it is built into the rite.

If your maternal grandparents had no son, or no one in their family performs śrāddha, the daughter's son or daughter (dauhitra) is traditionally named as a proper performer, and this is highly praised. Pitṛ Pakṣa even has a special day, Mātāmaha śrāddha, observed by many families on the first day of Āśvina's bright half.

You can do it on their death tithis, or in Pitṛ Pakṣa on the relevant tithi, or on Sarvapitṛ Amāvasyā if dates are unknown. Name them clearly during tarpaṇa — the remembrance is what carries.

Source: Dharmasindhu; Nirṇayasindhu (dauhitra as performer)

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