Ojha scored 99 off 116 balls and hit 16 fours and six before being stumped off legspinner Abhishek Jhunjhunwala's bowling.
Sent into bat, Madhya Pradesh lost two early wickets before Ojha and Devendra Bundela steadied the innings with a 127-run stand for the third wicket to push Bengal on to the backfoot at the Holkar Cricket Stadium.
Bundela contributed 61 off 157 balls and his innings contained eight fours and a six.
Udit Birla made 50 off 61 balls and hit seven fours.
At stumps, Rameez Khan was batting on 35 while giving him company was Jalaj Saxena, who was batting on 44.
Promising pacer Shami Ahmed was the only Bengal bowler to shine as he finished the day's play with figures of two for 50 in 20 overs. There was a wicket apiece for Jhunjhunwala and Veer Pratap Singh who bowled Bundela.
Brief scores:
Madhya Pradesh: 322 for 5 in 90 overs (Ojha 99, Bundela 61, Birla 50; Shami Ahmed 2/68)
