The 30-share Sensex soared to the day's high of 33,520.82, but profit-taking activity towards the end in heavyweights made the index settle at 33,342.80, up 235.98 points, or 0.71 per cent.
The gauge had rallied 346 points in the previous session.
The 50-share Nifty after racing past the key 10,300-mark during the day gave up some ground to close up 68.85 points, or 0.67 per cent, at 10,283.60.
For the week, the Sensex climbed 28.24 points, or 0.08 per cent, while the Nifty shed 38.15 points, or 0.36 per cent.
The rating upgrade came after a gap of 13 years - Moody's hadlast upgraded India's rating to 'Baa3' in 2004.