The effect of pre-treating Moringa oleifera leaf powder (MOLP) with different levels of polyethylene glycol (PEG) on the growth performance, serum biochemistry, hematology, and meat quality parameters of Jumbo quail was evaluated. Two-week-old quail chicks (n = 432; 239.6 ± 6.48 g live-weight) were randomly allocated to six diets formulated by incorporating (10% w/w) untreated MOLP (PEG0) or MOLP pre-treated with PEG at 2.5% (PEG25), 5% (PEG50), 7.5% (PEG75), and 10% (PEG100) (w/w) into a standard grower diet (CON). Overall feed intake linearly increased with PEG levels. At week 4, significant quadratic trends were recorded for weight gain and feed conversion efficiency (FCE) but, at week 5, FCE linearly declined as PEG levels increased. Hemoglobin, phosphorus, and albumin showed quadratic trends, while calcium and chroma (1 h post-mortem) linearly declined in response to PEG levels. Diet PEG50 promoted a higher shear force value (2.41) than diets PEG0 and PEG25. The PEG50 diet promoted a similar (p > 0.05) shear force as diet CON. Based on the quadratic response for weight gain, the optimal PEG pre-treatment level was calculated to be 5.9%. It was concluded that MOLP condensed tannins negatively affect growth performance and should be ameliorated to enhance the utility of this nutraceutical source for Jumbo quail.